Pulsed Doppler ultrasound detection of flow disturbances in arteriosclerosis.

Pulsed Doppler ultrasound blood flow detection has been used in a noninvasive manner to detect arterial abnormalities associated with arteriosclerosis. Sound spectrograms of ultrasound signals obtained from in vitro and animal studies in which flow was disturbed by obstacles placed in the flow stream showed a different distribution of energy over frequency than signals obtained from studies with no flow disturbances. Similar findings were seen clinically. A technique has been developed which can detect disturbed flow patterns resulting from partial occlusion in important superficial arteries (e.g. femoral and carotid) up to 15 cm distal to localized arterial wall abnormalities. Thirty-five arterial examinations of normal and arteriographically abnormal arteries in 12 patients revealed a sensitivity of 83 percent and a specificity of 61 percent. This study suggests that pulsed Doppler ultrasound may be useful as a screening technique for detection of arteriosclerotic lesions in major superficial arteries.     

彩色多普勒超声在下肢动脉闭塞性疾病中的应用

目的探讨彩色多普勒超声诊断下肢动脉闭塞性疾病中的价值。方法对32例经手术、MRI、DSA等证实的下肢动脉闭塞性疾病进行彩色多普勒超声检查，其中急性7例，慢性23例，2例为人造血管术后。仪器选用百胜AU-4。结果彩色多普勒能显示被栓动脉病变情况，包括狭窄、闭塞及侧枝等。本组彩超诊断下肢动脉闭塞性疾病的符合率为90．6％(29／32)。结论彩色多普勒超声能帮助提高下肢动脉闭塞性疾病的诊断准确性。     

Measurement of wave velocity in arterial walls with ultrasound transducers

Arterial wall stiffness can be associated with various diseases. The stiffness of an artery can be measured with the pulse wave velocity (PWV) using the "foot-to-foot" method. However, the foot of the pressure pulse is not very clear, due to reflected waves. The blood pressure pulse generated by the heart is a low frequency wave and its time resolution is low. PWV is an average indicator of artery stiffness between the two measuring positions; therefore, it cannot easily identify local stiffness. In this paper, a sinusoidally modulated force with a high frequency is generated noninvasively on the arterial wall by the radiation force of ultrasound (US). The resulting vibration in the artery is measured with an US Doppler transceiver. The wave velocity in the artery is measured from a wave image obtained by scanning the force transducer and fixing the sensor transducer. Because of the high imposed force frequency, the temporal resolution of this method is much higher than the conventional pressure PWV method. Local wave velocity more than a few millimeters can be measured, which is not possible with the PWV method.     

高血压病患者肺静脉血流的超声多普勒研究

应用脉冲多普勒技术对照研究了５８例正常人和５６例收缩功能正常的高血压病患者二尖瓣和肺静脉的血流频谱参数。结果显示：高血压病组二尖瓣舒张期血流参数Ｅｐ、Ｅｉ、Ｅ／Ａ较正常组显著降低，ＡＦＦ显著升高；其肺静脉血流参数Ｓｐ、Ｓｉ、ＳＦ显著升高而Ｄｐ、Ｄｉ显著降低，即心室收缩期肺静脉向左房的回流速度及回流分数增加，舒张期的回流则减慢。说明高血压病患者在心功能代偿期，不仅存在左室舒张充盈的异常，同时也存在肺静脉的回流异常。     

Measurement of pulse wave velocity using pulse wave Doppler ultrasound: comparison with arterial tonometry

Pulse wave velocity (PWV), the speed of propagation of arterial pressure waves through the arterial tree, is related to arterial stiffness and is an important prognostic marker for cardiovascular events. In clinical practice PWV is commonly determined by arterial tonometry, with a noninvasive pressure sensor applied sequentially over carotid and femoral arteries. The electrocardiogram (ECG) is used as a timing reference to determine the time delay or "transit time" between the upstroke of carotid and femoral pulse waveforms. Commercially available vascular ultrasound scanners provide a pulsed wave (PW) Doppler velocity signal, which should allow determination of carotid-femoral transit time and hence PWV. We compared carotid-femoral PWV measured by tonometry and by PW Doppler ultrasound (Seimens, Apsen scanner with 7 MHz linear transducer) in asymptomatic subjects (n = 62, 26 male, aged 21 to 72 y). To test for intra-subject and inter-observer variation, ten subjects were scanned by one observer on two occasions 2 wk apart and by two observers on same day. PWV by tonometry ranged from 5.3 to 15.0 m/s. There was no significant difference between mean values of PWV obtained by the two techniques (mean difference: 0.3 m/s, standard deviation of difference: 1.5 m/s), which were closely correlated (r = 0.83). The coefficient of variation for repeated measures on the same subject by the same observer was 10.1% and the inter-observer coefficient of variation was 5.8%. These results suggest a commercial ultrasound scanner can be used to measure PWV, giving results that are reproducible and closely correlated with those obtained by arterial tonometry. (E-mail: ben_yu.jiang@kcl.ac.uk).     

Comparison of methods of recording and analysis of Doppler blood velocity signals in normal subjects

Doppler blood velocity signals were recorded from the aorta and pulmonary artery in normal adults, children and premature infants, using three different pulsed, range-gated instruments. The tracings analyzed by three independent methods of spectral analysis with axially aimed transducers showed velocity patterns with a narrow range of frequencies (blunt velocity profile) with a constant acceleration of blood flow in early systole. A similar velocity pattern was seen in the premature infant's aorta in which the transducer beam was larger than the vessel insonated. We conclude that the normal velocity pattern in the central circulation is close to blunt, and that tracings obtained with transducers that insonate varying proportions of the vessel give similar signals.     

取样容积位置及大小变化对估测肺血流量的影响

为评价取样容积(SV)位置和大小对超声心动图估测肺血流量(Q_P)的影响,在36例先心病患者中,SV取0.22cm、1.79cm,分别置于肺动脉瓣下、瓣口、瓣上记录肺动脉血流频谱,根据频谱外包络线估测Q_p,并与心导管值对比。结果显示:SV为0.22cm、1.79cm时,肺动脉瓣下、瓣口、瓣上估测的Q_p间相差显著(P＜0.01),与心导管实测值显著相关(r=0.30-0.80);不同大小SV多普勒估测Q_p间差异显著(p＜0.05)。结论:应用肺动脉血流速度频谱外包络线,SV取0.22cm,置于肺动脉瓣口可准确地估测Q_p。     

Method for estimating the Doppler mean velocity waveform

Practical aspects of a method for estimating the mean velocity waveform for a CW ultrasound system are described. The method, based on the technique proposed by Gerzberg and Meindl (1977), generates an analog mean signal for both forward and reverse flow with an accuracy of better than ± 5%. Application of the circuit for arterial assessment are presented, and its potential use for determining carotid spectral broadening is considered.     

Flow velocity patterns in the carotid bifurcations of young, presumed normal subjects

Spectral analysis of pulsed Doppler velocity waveforms has been found useful as a diagnostic technique in the assessment of carotid artery disease. While spectral broadening of the velocity waveform obtained at center stream sites is usually associated with arterial disease, the present study describes spectral patterns resulting from disturbed blood flow in the proximal branches of the carotid bifurcation in young, presumed normal human subjects. In those studied, spectral patterns in the bifurcation region exhibit characteristics similar to those occurring in zones of flow separation in model studies under conditions of steady flow. It is important to distinguish the spectral patterns due to arterial disease from those occurring in the normal bifurcation. This paper describes the types of flow disturbances noted in presumed normal arteries and points out the need to understand the flow velocity patterns that may be found at specific anatomical sites across the carotid bifurcation.     

The Leicester Doppler Phantom—A Digital Electronic Phantom for Ultrasound Pulsed Doppler System Testing

Doppler flow and string phantoms have been used to assess the performance of ultrasound Doppler systems in terms of parameters such as sensitivity, velocity accuracy and sample volume registration. However, because of the nature of their construction, they cannot challenge the accuracy and repeatability of modern digital ultrasound systems or give objective measures of system performance. Electronic Doppler phantoms are able to make use of electronically generated test signals, which may be controlled precisely in terms of frequency, amplitude and timing. The Leicester Electronic Doppler Phantom uses modern digital signal processing methods and field programmable gate array technology to overcome some of the limitations of previously described electronic phantoms. In its present form, it is able to give quantitative graphical assessments of frequency response and range gate characteristics, as well as measures of dynamic range and velocity measurement accuracy. The use of direct acoustic coupling eliminates uncertainties caused by Doppler beam effects, such as intrinsic spectral broadening, but prevents their evaluation. (E-mail: john.gittins@uhl-tr.nhs.uk)     

组织多普勒成像法与脉冲多普勒法左室Tei指数测定的对比研究

目的利用组织多普勒成像与脉冲多普勒超声测量40例正常人和50例心脏病患者的左室Tei指数,探讨组织多普勒成像法所测左室Tei指数的可行性及与脉冲多普勒法所测左室Tei指数的一致性。方法1.在脉冲多普勒条件下,于心尖四腔观和心尖五腔观,获得二尖瓣口和主动脉瓣口血流频谱,测量二尖瓣口舒张期血流频谱止点到下一血流频谱起点时间(a)和主动脉瓣口收缩期血流频谱持续时间(b),Tei=(a-b)/b(Tei-1);2.在组织多普勒条件下,于心尖五腔观获得二尖瓣与主动脉瓣交汇处组织运动频谱,测量同一心动周期内的a和b,计算Tei指数(Tei-2)。结果正常组及心脏病组的Tei-1及Tei-2值均有显著性差异(0.37±0.05与0.69±0.17及0.41±0.03与0.73±0.17,均P<0.05);Tei-1与Tei-2值之间无显著性差异(0.37±0.05与0.41±0.03;0.69±0.17与0.73±0.17,均p>0.05)。正常组和心脏病组的Tei-1与Tei-2之间呈高度相关(r=0.751,P<0.001;r=0.942,P<0.001)。TDI及PW两组结果呈高度相关(r=0.973,P<0.001)。结论2种方法所测的左室Tei指数呈极高度相关。     

Effect of microbubble contrast on intracranial blood flow velocity assessed by transcranial Doppler

Purpose

Ultrasound contrast agents (UCA) salvage a considerable number of transcranial Doppler (TCD) exams which would have failed because of poor bone window. UCA bolus injection causes an undesirable increase in measured blood flow velocity (BFV). The effect of UCA continuous infusion on measured BFV has not been investigated, and some in vitro experiments suggest that gain reduction during UCA administration may also influence measured BFV. This study aimed to investigate the effect of UCA continuous infusion on BFV measured by TCD and the influence of gain reduction on these measurements in a clinical setting.

Methods

The right middle cerebral artery of ten patients with optimal bone window was insonated using a 2 MHz probe. UCA were administered using an infusion pump. BFV was measured (1) at baseline, (2) during UCA infusion, (3) during UCA infusion with gain reduction, and (4) after UCA wash-out phase. Gain reduction was based on the agreement between two neurosonographers on the degree of gain reduction necessary to restore baseline Doppler signal intensity (DSI). Actual DSI was estimated offline by analysis of raw data.

Results

BFV measured during UCA infusion with no gain adjustment was significantly higher than baseline BFV [peak systolic velocity (PSV): 85.1 ± 19.7 vs. 74.4 ± 19.7 cm/s, p < 0.0001; Mean velocity (MV): 56.5 ± 11.8 vs. 50.2 ± 12.3 cm/s, p < 0.0001]. BFV measured during UCA infusion with gain reduction was not significantly higher than baseline BFV (PSV: 74.3 ± 18.9 vs. 74.4 ± 19.4 cm/s, p = 0.8; MV: 49.4 ± 11.0 vs. 50.2 ± 12.3 cm/s, p = 0.8). Actual DSI during UCA infusion with gain reduction was not significantly higher than baseline DSI (13 ± 1 vs. 13 ± 1 dB).

Conclusion

This study shows that UCA continuous infusion leads to an increase in measured BFV which may be counteracted by reducing Doppler gain thus restoring pre-contrast DSI.     

彩色多普勒组织成像对高血压病左室舒张功能的研究

目的：探讨能客观地评价左室舒张功能（LVDF）的方法。方法：高血压病患者80例,其中左室充盈假性正常化（PN）12例,正常对照组40例,应用多普勒组织成像（DTI）及脉冲多普勒（PWD）技术检测二尖瓣环（P＜0.01）,其中DTI检测左室充盈假性正常化组二尖瓣环速度e/a、ei/ai比值及Eacc明显小于对照组（P＜0.01）。结论：DTI检测二尖瓣环运动速度之比评价LVDF优地二尖瓣口血流频谱。     

Comparison of blood velocity waveform indices recorded by pulsed Doppler and continuous wave Doppler in the umbilical artery

A comparison was made between the AB ratio, resistance index (RI), and pulsatility index (PI), calculated from tracings obtained by pulsed Doppler (PD) and continuous wave (CW) Doppler devices in 14 uncomplicated singleton pregnancies. The AB ratio, RI, and PI were a slightly higher for the CW Doppler compared to the PD system, although not significantly (p = 0.18, p = 0.21, and p = 0.44, respectively). The difference in signal to noise ratio (S/N ratio) between the PD and CW Doppler systems was felt to be the reason for the discrepancy in the calculated velocity waveform indices.     

The application of CCD transversal filters for real-time spectral analysis of Doppler ultrasound arterial signals

A method of Doppler spectral analysis, based on the use of charge-coupled device (CCD) transversal filters, is described in this paper. A brief discussion of current methods of real-time spectral analysis is included, followed by a review of the theoretical basis of CCD spectral analysis. The system is detailed and the results of performance and clinical tests are presented. Carotid artery Doppler waveforms produced using the analyser illustrate the effects of flow abnormalities on the blood flow velocity waveform.     

应用PDE检测正常胎儿心脏各瓣口血流速度

本研究应用脉冲多普勒超声心动图（PDE）检测正常胎儿心脏各瓣口峰值血流速度。将100例胎儿按孕周20～40周分为五组。PDE检测结果表明：胎儿心脏动脉瓣口血流呈单峰频谱，房室瓣口血流呈双峰频谱（E峰、A峰）；各瓣口峰值血流速度随孕周而增加，与孕周呈正相关，有统计学意义（P＜0．05）。PDE对于检测胎儿心脏血流，评价胎儿心脏功能具有重要作用。     

Doppler velocity histogram analysis of hepatocellular carcinoma

To study the characteristics of tumor blood flow, flow profiles from hepatocellular carcinomas (39 profiles) and normal hepatic arteries (23 profiles) were evaluated using velocity histograms obtained with Doppler ultrasound. The histograms were classified into three types: (1) high-peak, (2) flat, and (3) low-peak. Characteristically, the low-peak types and the flat types, with flows in opposing directions, were seen only in the tumor vessels. The turbulence in a phantom flow model was of the low-peak type. Spectral analysis revealed that the velocity profile of tumor blood flow was different from that of noncancerous flow and that tumor blood flow was characterized by turbulence. © 1995 John Wiley & Sons, Inc.     

Multichannel Pulsed Doppler Signal Processing for Vascular Measurements in Mice

The small size, high heart rate and small tissue displacement of a mouse require small sensors that are capable of high spatial and temporal tissue displacement resolutions and multichannel data acquisition systems with high sampling rates for simultaneous measurement of high fidelity signals. We developed and evaluated an ultrasound-based mouse vascular research system (MVRS) that can be used to characterize vascular physiology in normal, transgenic, surgically altered and disease models of mice. The system consists of multiple 10/20 MHz ultrasound transducers, analog electronics for Doppler displacement and velocity measurement, signal acquisition and processing electronics and personal computer based software for real-time and off-line analysis. In vitro testing of the system showed that it is capable of measuring tissue displacement as low as 0.1 μm and tissue velocity (μm/s) starting from 0. The system can measure blood velocities up to 9 m/s (with 10 MHz Doppler at a PRF of 125 kHz) and has a temporal resolution of 0.1 milliseconds. Ex vivo tracking of an excised mouse carotid artery wall using our Doppler technique and a video pixel tracking technique showed high correlation (R² = 0.99). The system can be used to measure diameter changes, augmentation index, impedance spectra, pulse wave velocity, characteristic impedance, forward and backward waves, reflection coefficients, coronary flow reserve and cardiac motion in murine models. The system will facilitate the study of mouse vascular mechanics and arterial abnormalities resulting in significant impact on the evaluation and screening of vascular disease in mice. (E-mail: areddy@bcm.edu)     

Color Doppler sonography of normal breasts: detectability of arterial blood vessels and typical flow patterns

In a prospective study, 200 healthy female breasts were examined using color Doppler sonography to study the detectability and the resistive indices (RIs) of arterial vessels. In each breast, we attempted to detect two to three vessels and recorded the frequency spectrum with RI of each vessel. Blood vessels (n = 522) could be demonstrated in 196 (98%) breasts. Continuous diastolic flow (RI < 1) was found in 520 (99.6%) vessels. The mean RI of premenopausal women was 0.64; that of postmenopausal women was 0.70. This difference is highly statistically significant (p < 0.0001), but there is a marked overlap between the RIs of both groups. The variation in RI values of all women (up to 0.45), as well as in the breasts of the same woman (up to 0.31), was considerable. We conclude that modern color Doppler devices permit the detection of blood flow in the breast with regularity. Continuous diastolic flow (RI < 1) is a typical flow pattern. The variations of RI between women, and even for the same woman, are remarkable. The mean RI of premenopausal women is lower than the value for postmenopausal women.